Storage tanks are used throughout the world for storing various liquids in bulk form. In particular, storage tanks are used extensively for the storage of liquid gasoline at retail gasoline stations. Necessarily, these stations are in populated areas and, therefore, there is always a danger associated with leaks from the tanks. Leaked gasoline poses a hazard to the environment as well as an obvious health hazard. The known problem is particularly troublesome in that gasoline storage tanks are usually buried underground and any leaks which develop are normally very slow initially.
Underground storage tanks are particularly troublesome in those areas that are prone to earthquakes. Typical underground storage tanks are constructed of metal or fiberglass reinforced resin. Any earthquake is likely to cause a crack in the tank with a consequent leak. If the leak is slow, the same problems as above discussed exist. If the leak results in a large sudden loss, the problem is readily detected, but only after it is too late.
The problems associated with the present underground storage tanks are well known. Various attempts have been made to alleviate the problems. In my U.S. Pat. No. 4,523,454 there is described a liquid storage tank system using a flexible jacket for secondary containment means and various leak detection means associated with a closed space between the storage tank and flexible jacket. The leak detection means monitors for leaks of the inner tank and/or jacket. One described leak detection means comprises detecting fluid in the closed space and a standpipe/sight glass in communication with the closed space for observing any change in level or color of the detecting fluid. While such a detection means is economical and reliab1e, there are various drawbacks associated with it. For example, a standpipe must be properly installed and maintained. Additionally, the system can be tampered with by a service station owner who is not concerned with what he may view as inconsequential leaks. A system having the advantages of the detecting fluid concept without its disadvantages would fill a need.
There has now been discovered a tank storage system which improves upon the existing systems. The system of this invention is economical and provides a certain measure of protection not available previously.